Vapor recovery system



y 1941- P. J. HARRINGTON ETAL 2,242,299

VAPOR RECOVERY SYSTEM Filed May 15, 1940 SECONDARY c004 nvG i I I a. i

a L 6 f /N/ 7-1.4 L l J c L EXPAND/Arc u- We COMPREss/NC wwr 124 Irv/Arc (o/ 17 125.55 104/ 5N6 IIVE raw-1) VA Po 7: 7'0 AIR l ms [lg 5 13%)?! f2 1 Patented May 20, 1941 VAPOR. RECOVERY SYSTEM Paul J. Harrington, Mountainside, and George D. Priestman, Hillside, N. J., assignors to Standard Oil Development Company, a corporation of Delaware Application May l5, 1940, Serial No. 335,402

Claims.

The present invention is concerned with the recovery of vaporous constituents from gases containing the same. The invention is more particularly directed to an improved process and apparatus comprising compressing, and expanding stages by which valuable petroleum hydrocarbon constituents, particularly those constituents which may be included in motor fuels and utilized in polymerization, alkylation and related processes are recovered. In accordance with the present process feed gases containing recoverable vaporous constituents are passed through a compression zone. The come pressed gases are cooled in an initial cooling zone with water or equivalent means and further cooled in a secondary cooling zone with expanded gases. The cooled compressed feed gases are coolin passed from the secondary cooling zone to a vaporous constituents from gas mixture in order to prevent the loss of the same. For example, in the refining of petroleum oils in which volatile motor fuels and similar oils'are stored in vaportight cone roofs, pressure or equivalent tanks and the like, an appreciable quantity of the oil is lost in the vapors expelled from the tanks as a result of filling the tanks or due to the. expansion of vapors in the tanks with daily temperature changes. Methods which have been pro.

,posed for recovering at least a portion of the'val- 'uable vaporous constituents contained in the gases vented from the tanks include various oil absorption operations as well as processes in which, the vented gases are compressed and cooled in order to condense the vaporized valuable constituents. These processes however are rela tively expensive, which materially raises the overall manufacturing costs. Furthermore, in many instances it is uneconomical'to recover these vaporized constituents which thus representsadirect loss. I

We have now discovered an improved process comprising compressing, cooling; separating, ex-

The process of our invention may be readily understood by reference to the attached drawing illustrating modifications of the same. For purpose of illustration it is assumed that the vapors comprise'vapors expelled from vessels and tanks utilized in the storing and processing of finished petroleum oils boiling in the motor fuel boiling range. These vapors mixed with air or other gases employed in repressing operations, as for example an inert gas or a'natural gas are withdrawn from tank I by means of line 2. It is to be understood that tank I may comprise any type or number of tanks arranged in any suitable manner. The gases are passed through compressing zone 3, the power being supplied from expanding engine 4 and gas combustion engine 5. The compressing zone 3 may comprise a single two-stage compressor, in which the power for one stage is supplied by expanding engine 4, and the power for the other' stage is supplied from gas combustion engine 5. Compressing zone 3 may likewise comprise two individual compressors in which the power for one is supplied by expanding engine 4 and in which the power for the other is supplied by gas combustion engine 5. It is to be understood that any desirable arrangement of the individual stages of the compressors, or arrangement and number of the compressors may be utilized. The

compressed gases are withdrawn from compressing zone 3 by means of line 6 and-passed into an initial cooling zone I, the cooling medium preferably being water. The partially cooled compressed gases are withdrawn from initial cooling zone I by means of line 8 and passed into a secondary cooling zone 9, the cooling medium of which is cooled vapors derived from a source hereinafter explained. The cooled gases are withdrawn from secondary cooling zone 9 by means cf-line' Ill and passed into a separation zone ll wherein a separation is made be-, tween the liquid condensate and the uncondensed gases and vapors. The condensed liquid is withdrawn from separation zone H by means of line I! and handled inany manner desirable,

preferably returned to the tank or tanks from which the vapors have beenevolved or utilized for blending infinished products. The desired liquid level is maintained in separation zone H by means of a float controlvalve arrangement it. The uncondensed gases are withdrawn from separation zone H by means of vapor line M. and utilized as a driving medium in expanding engine t. The power of engine d is transmitted by suitable means is and utilized as a driving force for compressor 3. The expanded vapors are withdrawn from expanding engine t by means of line it and passed through heat exchanger 9 wherein the chilled expanded vapors cool the compressed feed gases in the secondary cooling zone. The expanded vapors are withdrawn from secondary cooling zone 9 by means of line H and utilized as the driving fuel for gas combustion engine 5. The power from gas combustion engine is transmitted by suitable means l8 and employed as the driving power for compressor 3. The spent vapors are withdrawn from gas engine 5 by means of line H! and disposed of in any suitable manner. Excess vapors which cannot be utilized in gas engine 5 are withdrawn from the system by means of line 20 and likewise handled in any desirable manner.

The process of the present invention may be widely varied. The invention essentially comprises an improved system utilizing a novel arrangement of compressing, cooling, separating, expanding and burning zones by which valuable vaporized constituents may be readily and efficiently recovered from gas mixtures containing the .same. In accordance with the present process it is possible to economically justify the recovery of recoverable vaporized petroleum hydrocarbon constituents which otherwise would be lost. By employing the particular combination of an expanding engine, a gas engine and compressor in combination with a two-stage cooling operation as disclosed appreciable advantages are secured.

The extent to which the feed gas mixture is cooled in the respective cooling zones will be a function of the composition of the particular feed gas mixture being processed, the extent to which the feed gas is compressed in the compression zone, and the extent of recovery desired. For example, when processing vapors evolved from motor fuels in storage, it is desired to compress the gases to a pressure in excess of 250 pounds per square inch, preferably to a pressure of approximately 300 pounds per square inch. It is then preferred to cool the compressed gases in the initial cooling zone to-a temperature below about 100 F. and to cool the gases in the secondary cooling zone to a temperature below about 50 F., preferably to a temperature below about 40 F.

In order to further illustrate the invention, the following example is given which should not be construed as limiting the invention in any manner whatsoever.

Example In one operation a gaseous mixture of about the following composition evolved from petroleum oils boiling in the motor fuel boiling range was collected and handled as follows: Per cent Air 70 Butanes 15 Pentanes 10 Hexanes and heavier 5 the storage tank I F. and at about perature of the compressed gases was about 350 F. The compressed gases were then passed through an initial cooling zone in which the temperature of the same was lowered to about 95 F. by means of salt water introduced at a temperature of 70 F. and withdrawn at a temperature of about 85 F. The partially cooled gases were passed through a secondary cooling zone in which the temperature of the same was lowered to about 35 F. The cooled gases were then passed into the separation zone at a pressure of about 300 pounds per square inch in which approximately 90% of the butanes and higher boiling constituents were condensed. The condensate was recycled to the storage tanks from which the vapors were withdrawn. The uncondensed vapors were withdrawn from the separation zone and passed through an expanding engine, the power of which was utilized in running the compressors in the compression zone. The expanded vapors at a pressure of about 25 pounds per square inch and at a temperature of about -50 F. were passed through the secondary cooling zone and utilizedin cooling the compressed vapors as described. The expanded vapors were then passed to a gas combustion engine and utilized as a driving medium, the power of which was employed to supply power to the compressors in the compression zone.

In another operation an identical gaseous mixture was processed according to current practice and compressed to a temperature of about 300 pounds per square inch gauge. The compressed gases were then cooled by means of cooling water to a temperature of about 95 F. Under these conditions only about 60% of the butanes and higher boiling constituents were condensed. In

' addition, this latter operation was more expensive, as represented by the additional cost of driving the compressor by steam driven prime mover.

In the present process a portion of the work of compression is obtained by the expansion of the compressed, cooled and separated gas, while the residual amount of energy is obtained by burning a portion of the lean gas in the gas combustion engine part of the compression drive.

The present invention is not to be limited by any theory or mode of operation, but only in and by the following claims in which it is desired to claim all novelty in so far as the prior art permits.

We claim:

1. Process for the segregation and recovery of vaporized constituents from a feed gas mixture comprising compressing the feed gas mixture in a compression zone,.cooling the compressed feed gas mixture in an initial cooling zone, further cooling the partially cooled feed gas mixture in a secondary cooling zone, passing the cooled feed gas mixture to a separation zone wherein a separation is made between liquid condensate and uncondensed gases, expanding said uncondensed gases under conditions whereby the evolved gases is materially lowered, passing the expanded relatively cold uncondensed gases in heat exchange with said feed gas mixture in said secondary cooling zone, withdrawing said expanded cooled uncondensed gas from said secondary cooling zone and burning the same in a gas combustion engine under conditions whereby the expended energy is utilized for the compression amazes of said feed gas mixture in said compression zone and recovering liquid condensate from said separation zone.

2. Process for the segregation and recovery of vaporized petroleum oil constituents which boil in the motor fuel boiling range from a. feed gas mixture containing the same which comprises compressing the feed gases in an initial stage, cooling the compressed gases in a secondary stage by means of cooling water, further cooling the partially cooled gases in a tertiary stage by means of expending the cooled gases, separating the condensate from uncondensed gases in a separation zone, expanding said uncondensed gases in an expanding engine under conditions whereby the energy evolved is utilized for the compression of the said gas mixture in said initial stage, passing the cool expanded vapors from said expanding engine in heat exchange with said feed gases in said tertiary stage, withdrawing said vapors from said tertiary stage, and burning the same in a gas combustion engine under conditions whereby the expanded energy is utilized for the compression of said feed gases in'said initial stage and recovering liquid condensate from said separation zone.

3. Process in accordance with claim 2 in which said gases are compressed in said initial stage to a pressure of about 300 pounds per square inch, in which said gases are cooledby means of cooling water in said secondary stage to a temperature below about 100, F., and in which said gases are cooled in saidtertiary stage by means of expanded cooled vapors to a temperature below about 40 F.

4. Process for the recovery of hydrocarbons boiling in the boiling range of hydrocarbons having 4 carbon atoms in the molecule and higher from gases comprising vapors evolved from petroleum oils boiling in the motor fuel boiling range which comprises compressing the gases in a compression zone-to a pressure in excess of about 250 pounds per square inch, cooling the compressed gases in an initial cooling zone by means 01' cooling water to a temperature below about 100 F., further cooling the partially cooled gases in a secondary cooling zone by means of expanding the cooled vapors to a temperature below about 40 F., passing the cooled gases to a separation zone and separating aliquid condensate from uncondensed gases, expanding said uncondensed gases under conditions whereby the energy evolved is utilized or the compression of said feed gases in said compresliquid hydrocarbons from feed gas mixtures containing'the same which comprises means .for collecting and passing the feed gas mixture to a compression zone, compression means in said compression zone for compressing the feed gas mixture, means for passing the feed gas mixture from said compression means to cooling means comprising an initial and secondary cooling zone, means for passing water in heat exchange with said gases in said initial cooling zone, means forv passing expanded vapors in heat exchange with the feed gases in said secondary cooling zone, means for conducting the feed gas mixture from said secondary cooling zone to separation means for efiecting separation between vapors and condensate, means for conducting the separated vapors'from the separation means to means for expanding the gases which comprises an expanding engine, means for utilizing the power evolved from the expanding means for driving said compression means, means for withdrawing the expanded vapors from said expanding means and for passing the expanded vapors in heat exchange with the Ieed gas mixture in said secondary cooling zone, means for withdrawing the expanded gases from the secondary cooling zone and means for burning the same which comprises a gas combustion engine, means for transmitting the power evolved from said gas combustion engine to said compression means, and means for withdrawing a liquid condensate product from said separation zone.

' PAUL J. HARRINGTON.

GEORGE D. PRIES'I'MAN. 

